US11343900B2 - Thin-film target for DT neutron production - Google Patents
Thin-film target for DT neutron production Download PDFInfo
- Publication number
- US11343900B2 US11343900B2 US16/930,514 US202016930514A US11343900B2 US 11343900 B2 US11343900 B2 US 11343900B2 US 202016930514 A US202016930514 A US 202016930514A US 11343900 B2 US11343900 B2 US 11343900B2
- Authority
- US
- United States
- Prior art keywords
- film
- target
- thin
- tritide
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active, expires
Links
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H6/00—Targets for producing nuclear reactions
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
- G21G4/00—Radioactive sources
- G21G4/02—Neutron sources
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H3/00—Production or acceleration of neutral particle beams, e.g. molecular or atomic beams
- H05H3/06—Generating neutron beams
Definitions
- the present invention relates to DT neutron production and, in particular, to a thin-film target for DT neutron production.
- a standard method for producing 14 MeV neutrons is to use the 3 H( 2 H,n) 4 He (i.e., T(D,n) ⁇ ) nuclear reaction with a deuterium (D) ion beam on a thick metal-tritide target.
- D deuterium
- the present invention is directed to a thin-film target for DT neutron production, comprising a substrate comprising a high D permeability material, a permeation barrier layer comprising a low D permeability material on the substrate to inhibit D permeation from the substrate therethrough, and a front-surface tritide layer on the permeation barrier layer that reacts with an incident D beam to produce DT neutrons, wherein the combined thickness of the tritide layer and the permeation barrier layer is less than the range of the incident D beam.
- the D permeability of the permeation barrier material is at least five orders-of-magnitude less than that of the substrate material.
- the thicknesses of the tritide and the permeation barrier layer can be selected to simultaneously maximize T(D,n) ⁇ reaction yield in the tritide layer, maximize D implantation into the substrate, and minimize D permeation from the substrate through the permeation barrier layer to the tritide layer.
- the life time of thick- and thin-targets were compared for production of 14 MeV neutrons by the T(D,N) ⁇ nuclear reaction.
- the target life was maximized by operating a titanium tritide target at a temperature of 150° C., where diffusion is fast enough that the implanted D mixes with the tritium throughout the entire thickness of the film.
- the neutron production rate decreased with time as expected due to isotope exchange of tritium in the film with the implanted deuterium, and the number of neutrons obtained from a target is proportional to the initial tritium content of the film.
- the thin-film target of the present invention the incident deuterium is implanted through the tritide and into the underlying substrate material.
- a thin permeation barrier layer between the tritide film and substrate reduces the rate of tritium loss from the tritide film. Solubility, diffusivity, and permeability of deuterium are important properties in choosing suitable materials for the barrier and substrate. As an example, good thin-film target performance was achieved using W and Fe for the barrier and substrate materials, respectively.
- the thin-film targets can produce similar number of neutrons as thick-film targets while using only a small fraction of the amount of tritium.
- FIG. 1 is a schematic illustration of a setup to produce DT neutrons from a thick-film target for neutron irradiation of a test device.
- FIG. 2 is a graph of the neutron yield (solid curve) and range profile (dashed curve) for 135 keV D on TiT 1.8 .
- FIG. 3 is a graph of neutron production rate, determined from yield of associated alpha particles, versus time of D beam exposure for a thick-film target.
- FIG. 4 is a graph of neutrons produced versus incident deuterium, measured (solid curve) and fit to the isotope exchange model (dashed curve).
- FIG. 5 is a graph of depth profile of implanted D from a SRIM simulation for the thin-film target configuration (dashed curve) and the DT reaction yield vs depth for a thick tritide target (solid curve).
- FIG. 6 is a graph of permeability of deuterium in various metals vs reciprocal temperature.
- FIG. 7 is a schematic illustration of the permeation model for the relative flux of D through the permeation barrier and substrate giving Eq. (4).
- FIG. 8 is a graph of neutron yield vs integrated beam current. Solid lines show data from four thick-film targets and dashed lines show data from six thin-film targets with a W permeation barrier and an Fe substrate.
- FIG. 1 shows a setup for producing DT neutrons from a standard thick-film for neutron irradiation of a test device.
- the thick-film target comprises a 5- ⁇ m thick titanium tritide film on a copper substrate.
- a 270 keV D 2 + ion beam can be focused and rastered on the target for uniform D flux.
- the thick-film target temperature is typically controlled at 150° C. during operation.
- Neutron production rate and fluence can be independently determined by a variety of diagnostics.
- the neutron production rate can be determined in real time from the alpha yield measured by a silicon detector.
- Neutron flux can also be measured directly in real time with a diamond detector that can have a flexible location outside of the target vacuum chamber.
- Total fluence can be determined by measuring dosimetry foil activity at the end of irradiation.
- initial reaction yield can be calculated from the DT reaction cross section, D beam current, and initial tritium content of the film.
- the ‘thick-film’ target uses a tritide film whose thickness is greater than the range of the incident deuterium.
- the lifetime is increased by operating the target at an elevated temperature where the diffusivity of D and T in the tritide film is sufficiently fast that the two isotopes continuously mix throughout the entire thickness of the film by thermal diffusion. Isotope exchange then occurs with the entire tritium content of the film, whereas at lower temperature the exchange occurs only within the range of implantation.
- tests with thick-film targets confirm that the change in the rate of neutron production versus time agrees with a dilution model based on isotope exchange and isotope mixing by diffusion.
- the number of neutrons that can be produced from a thick-film target is proportional to the initial quantity of T in the target undergoing exchange.
- a ‘thin-film’ target uses a tritide film that is thin enough so that the incident D passes through it and is implanted into the underlying substrate material.
- thermal diffusion of implanted D back into the tritide film is inhibited by a thin barrier layer with low D permeation between the tritide and substrate, and by using a substrate material in which D permeation is high.
- This invention reduces the rate of tritium loss from the thin-film target and therefore extends the target lifetime.
- the use of a thin tritide film reduces the quantity of T in the target and the quantity of T used during operation of the neutron production facility.
- An essential new feature of the present invention is the permeation barrier between the tritide film and the substrate. Without this barrier, D implanted into the substrate would diffuse to the tritide, since that is by far the shortest diffusion path for release, where it would mix with T and cause a similar high rate of T loss as from a thick-film target. Selection of the type of material for the substrate and the barrier is critical to the performance of the novel thin-film target and is driven by the diffusivity and solubility of D and other criteria, as described below.
- Exemplary thin-film tritide targets were fabricated using various materials for the substrate and permeation barrier. The neutron production rate versus time was measured for these thin-film targets and compared to that of thick-film targets. With a suitable choice of materials, the lifetime of thin-film targets can equal or exceed that of thick-film targets while using a small fraction of the amount of tritium per target.
- FIG. 2 shows the D range profile (dashed curve) for a D energy per atom of 135 keV, calculated from the SRIM particle transport code. See J. F. Ziegler et al., SRIM—The Stopping and Range of Ions in Matter (2008). Also shown is the DT nuclear reaction yield (solid curve), i.e.
- the neutron yield decreases with time of D beam exposure, due to displacement of tritium by D implanted from the beam.
- the total concentration of D+T is limited to that of the dihydride phase. See W. M. Mueller et al., Metal Hydrides , Academic Press (1968).
- D is implanted, an equal quantity of D+T is released from the film.
- the DT isotope exchange occurs within a fraction of the total film thickness, since at lower temperatures the time for DT mixing by thermal diffusion is longer than the time for T loss by isotope exchange within the 1 ⁇ m range of D.
- raising the target temperature to 150° C.
- Target lifetime is increased further by focusing and rastering the D beam to obtain uniform average beam current density over the entire area of the tritide film. Beam focusing can use a magnetic quadrupole lens and electromagnetic deflection can be used to raster the beam over the target in horizontal and vertical directions.
- the neutron production rate is proportional to the tritium concentration which is uniform throughout the film and decreases as deuterium is added and tritium is lost from the reservoir, which is a classic dilution problem.
- N T N ⁇ ⁇ exp ⁇ ⁇ ( - N Di N ) ( 1 ) decreases exponentially with the amount of implanted deuterium N Di .
- the number of neutrons N n produced per incident D is given by:
- N N D +N T is the quantity of D+T in the film which is also the initial quantity of tritium (the total number of D+T atoms in the target is constant, as determined by the stoichiometry and volume), and ⁇ is the initial rate (neutrons per incident D) whose value is given in FIG. 2 .
- the integrated number of neutrons produced is:
- N n ⁇ ⁇ ⁇ N ⁇ ⁇ ( 1 - exp ⁇ ⁇ ( - N Di N ) ) ( 3 )
- the solid curve in FIG. 4 shows the experimentally observed integrated number of neutrons produced, determined from the alpha yield, versus integrated beam charge, which is proportional to N Di .
- the total number of neutrons produced was 2.2 ⁇ 10 15 .
- the total neutron fluence was about 3 ⁇ 10 12 /cm 2 at a test location just outside the test chamber 3 inches from the source. Many other tests with similar targets gave very similar results. Since the neutrons are emitted nearly isotropically, the neutron flux at a test location is close to that from a point source at distances greater than the diameter of the source. See J. Csikai, CRC Handbook of Fast Neutron Generators , Vol 1, CRC Press (1987).
- the dashed curve in FIG. 4 is a fit of Eq.
- the value of N obtained from this fit is within 10% of the value calculated from the atomic density of T times the volume of the tritide film.
- the excellent quantitative agreement validates the isotope exchange model for target lifetime.
- the model shows that the number of neutrons that can be obtained from a target ⁇ N can be increased only by increasing N, the initial quantity of T in the target, i.e the volume of the tritide film.
- the thick-film targets have the drawbacks that they must be replaced after a few days of use and they release about 7 Curies of tritium per target during use.
- the present invention is directed to a novel thin-film target that provides a longer target lifetime with less tritium usage.
- These thin-film targets use a tritide film thin enough so that most of the incident D passes through it and is implanted into a substrate material in which D can rapidly diffuse.
- An exemplary thin-film target that was developed and tested is shown in FIG. 5 .
- This exemplary target used a titanium tritide film 0.4 microns thick and with the same lateral dimensions as the thick-film target, 2 cm diameter for the tritide film and 2.5 cm diameter for the substrate.
- an essential new feature of the thin-film target of the present invention is an additional thin layer of material between the tritide film and the substrate which has very low permeability for hydrogen. This layer acts as a permeation barrier and impedes diffusion of deuterium from the substrate into the tritide.
- the implanted D would diffuse to the tritide, since that is by far the shortest distance, and cause tritium release.
- Selection of the type of material for the substrate and barrier is critical and is dictated by diffusion and solubility of D and other criteria. As shown in FIG. 5 , only a few percent of the implanted D stop in the tritide film. Therefore, if the permeation barrier prevents diffusion of D from the substrate to the tritide film, these thin-film targets can have a lifetime longer than the thick-film targets and use only a fraction of the tritium.
- the substrate material into which the D is implanted preferably meets the following criteria:
- FIG. 7 A permeation model, helpful in guiding selection of materials, is illustrated in FIG. 7 .
- the dashed lines schematically illustrate the steady-state concentration of D diffusing through the permeation barrier to the tritide (c b ) and to the back of the substrate (c s ).
- the ratio of D fluxes through the barrier and substrate is given by:
- D b and D s are the diffusion coefficients of D in the barrier and substrate materials, respectively. Since the concentrations c b and c s of D on either side of the interface are in local thermal equilibrium, their ratio is equal to the ratio of their solubilities.
- the ratio of fluxes ⁇ b / ⁇ s is therefore given by the ratio of D permeability P b /P s divided by the ratio of thickness x b /x s of the barrier and substrate.
- FIG. 8 shows a representative selection of target test results as the cumulative number of neutrons produced vs integrated D ion beam current, which is proportional to the number of incident D atoms.
- Plotting neutron yield versus integrated beam current instead of elapsed time facilitates comparison between targets by removing intervals when the beam was off, which varied from target to target.
- Neutron production was determined from the yield of associated alpha particles. Beam current was measured on the target as well as upstream into a Faraday cup with secondary electron suppression. Precision of the measurements of neutron yield and beam current are within 10%. The neutron yield was independently confirmed by foil activation dosimetry.
Landscapes
- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- High Energy & Nuclear Physics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Particle Accelerators (AREA)
Abstract
Description
decreases exponentially with the amount of implanted deuterium NDi. The number of neutrons Nn produced per incident D is given by:
where N=ND+NT is the quantity of D+T in the film which is also the initial quantity of tritium (the total number of D+T atoms in the target is constant, as determined by the stoichiometry and volume), and σ is the initial rate (neutrons per incident D) whose value is given in
-
- a) The thermal conductivity should be high to avoid thermal desorption of the tritium due to target heating by the beam,
- b) The diffusivity of D should be high enough at the temperature of operation to avoid accumulation of high concentrations at the depth of implantation.
- c) The solubility for deuterium should not be too low, so that the implanted D does not precipitate into gas bubbles, which tends to occur when D is implanted into materials in which the solubility and diffusivity of D are both low. D2 gas bubble growth and coalescence can result in exfoliation of the tritide film.
- d) Solubility of T in the substrate material should be low so that the titanium tritide film can be loaded by thermal equilibration with tritium gas at high temperature, without also excessively loading the substrate material.
In addition, the permeability of D should be high in the substrate and low in the barrier material. Permeability is the product of solubility and diffusivity. Table 1 andFIG. 6 summarize the solubility S, diffusivity D, and permeability P=SD of deuterium (or hydrogen) for a few candidate materials in the limit of low concentration, parameterized as a prefactor and thermal activation energy:
S=S o exp(−Q S /kT),
D=D o exp(−Q D /kT).
One caveat is that measurements of solubility and diffusivity are often made at higher temperatures, particularly for the low-permeability refractory materials, so extrapolation to the lower temperatures of interest here (approximately 30 to 150° C.) can introduce uncertainty. Therefore, data on solubility and diffusivity can be used as a qualitative guide for material selection, but probably not for quantitative prediction of thin-film target performance.
TABLE 1 |
Prefactor and activation energy for solubility |
and diffusivity of D (or H) in material. |
D0 | QD | S0 | QS | ||
Material | (cm2/s) | (eV) | (at frac)/atm1/2 | (eV) | |
Pd | 2.90E−03 | 0.23 | 0.0017 | −0.082 | |
Ni | 5.27E−03 | 0.401 | 0.0016 | 0.147 | |
Cu | 7.30E−03 | 0.382 | 0.0024 | 0.415 | |
Mo | 2.40E−04 | 0.109 | 0.0357 | 0.678 | |
Fe | 7.50E−04 | 0.105 | 0.002 | 0.297 | |
Cr | 3.00E−04 | 0.077 | 0.051 | 0.59 | |
Co | 9.30E−04 | 0.241 | 0.0019 | 0.239 | |
W | 4.10E−03 | 0.39 | 0.0089 | 1.042 | |
See N. R. Quick and H. H. Johnson, Acta. Metall. 26, 903 (1978); J. Volkl and G. Alefeld, “Hydrogen in Metals I: Basic Properties,” Topics in Applied Physics Vol 28, Springer Verlag (1978); R. Frauenfelder, J. Vacuum Sci. Technol. 6, 388 (1969); and “The Diffusion of H, D and T in Solid Metals,” Chapter 9 pgs 504-573 of Diffusion in Solid Metals and Alloys, editor H. Mehrer, Springer Verlag, Heidelberg, 1990.
where Db and Ds are the diffusion coefficients of D in the barrier and substrate materials, respectively. Since the concentrations cb and cs of D on either side of the interface are in local thermal equilibrium, their ratio is equal to the ratio of their solubilities. The ratio of fluxes ϕb/ϕs is therefore given by the ratio of D permeability Pb/Ps divided by the ratio of thickness xb/xs of the barrier and substrate. With barrier and substrate thicknesses of 0.1 μm and 0.1 cm, the requirement on permeabilities for a thin-film target to have a longer lifetime than a 10× thicker thick-film target becomes Pb/Ps<10−5 (i.e. less than 10% of the implanted D permeates through the barrier to the tritide film). This is a demanding criterion for a permeation barrier but can be achieved as shown in
Claims (5)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US16/930,514 US11343900B2 (en) | 2019-07-17 | 2020-07-16 | Thin-film target for DT neutron production |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201962875328P | 2019-07-17 | 2019-07-17 | |
US16/930,514 US11343900B2 (en) | 2019-07-17 | 2020-07-16 | Thin-film target for DT neutron production |
Publications (2)
Publication Number | Publication Date |
---|---|
US20210022237A1 US20210022237A1 (en) | 2021-01-21 |
US11343900B2 true US11343900B2 (en) | 2022-05-24 |
Family
ID=74346313
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/930,514 Active 2040-10-06 US11343900B2 (en) | 2019-07-17 | 2020-07-16 | Thin-film target for DT neutron production |
Country Status (1)
Country | Link |
---|---|
US (1) | US11343900B2 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN113573458B (en) * | 2021-06-11 | 2024-06-25 | 中科超睿(青岛)技术有限公司 | Nano gradient neutron target and preparation method thereof |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3320422A (en) * | 1963-10-04 | 1967-05-16 | Nra Inc | Solid tritium and deuterium targets for neutron generator |
US3646348A (en) * | 1968-08-08 | 1972-02-29 | Commissariat Energie Atomique | Neutron-emitting tritiated target having a layer containing tritium and a passive support with an intermediate barrier |
US4298804A (en) * | 1978-10-13 | 1981-11-03 | U.S. Philips Corporation | Neutron generator having a target |
-
2020
- 2020-07-16 US US16/930,514 patent/US11343900B2/en active Active
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3320422A (en) * | 1963-10-04 | 1967-05-16 | Nra Inc | Solid tritium and deuterium targets for neutron generator |
US3646348A (en) * | 1968-08-08 | 1972-02-29 | Commissariat Energie Atomique | Neutron-emitting tritiated target having a layer containing tritium and a passive support with an intermediate barrier |
US4298804A (en) * | 1978-10-13 | 1981-11-03 | U.S. Philips Corporation | Neutron generator having a target |
Non-Patent Citations (1)
Title |
---|
Hughey, B.J., "A long-lived tritiated titanium target for fast neuron production," Nuclear INstruments and Methods in Physics Research B 95 (1995), pp. 393-401. |
Also Published As
Publication number | Publication date |
---|---|
US20210022237A1 (en) | 2021-01-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Ueda et al. | Baseline high heat flux and plasma facing materials for fusion | |
Hatano et al. | Deuterium trapping at defects created with neutron and ion irradiations in tungsten | |
Markelj et al. | Displacement damage stabilization by hydrogen presence under simultaneous W ion damage and D ion exposure | |
Garner et al. | Determination of helium and hydrogen yield from measurements on pure metals and alloys irradiated by mixed high energy proton and spallation neutron spectra in LANSCE | |
Ma et al. | Free surface impact on radiation damage in pure nickel by in-situ self-ion irradiation: can it be avoided? | |
US11343900B2 (en) | Thin-film target for DT neutron production | |
Kapser et al. | Influence of sub-surface damage evolution on low-energy-plasma-driven deuterium permeation through tungsten | |
Qiao et al. | Erosion and fuel retentions of various reduced-activation ferritic martensitic steel grades exposed to deuterium plasma | |
Davies et al. | The use of α-spectroscopy for studying anodic oxidation | |
Myers et al. | Ion-beam profiling of 3 He in tritium-exposed type 304l and type 21-6-9 stainless steels | |
Markelj et al. | The effect of nanocrystalline microstructure on deuterium transport in displacement damaged tungsten | |
Wagemans et al. | The 17 O (n, α) 14 C reaction from subthermal up to approximately 350 keV neutron energy | |
Logan et al. | RTNS-II-a fusion materials research tool | |
Založnik et al. | Deuterium retention in MeV ion-irradiated beryllium | |
Alimov et al. | Deuterium retention in reduced activation ferritic/martensitic steel EUROFER97 exposed to low-energy deuterium plasma | |
Wampler et al. | Optimization of target lifetime for production of 14 MeV neutrons | |
Wampler et al. | 14 MeV DT Neutron Test Facility at the Sandia Ion Beam Laboratory. | |
Walker | Electron irradiation of beryllium oxide | |
Mitu et al. | Manufacturing and characterization of targets at IFIN-HH: developing an interdisciplinary body of knowledge | |
Causey et al. | Tritium inventory and permeation in the ITER beryllium | |
Golubeva et al. | Selective Sputtering of Steel EK-181 (Rusfer) | |
Türler | The expansion of the periodic table to its natural limits | |
McCracken | Recycling and surface erosion processes in contemporary tokamaks | |
Elenbaas | The effect of isotope exchange on deuterium retention in tungsten under ITER-like conditions | |
Damcott | The use of proton irradiation in the examination of radiation induced segregation in multicomponent alloys |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: BIG.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
AS | Assignment |
Owner name: NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA, LLC, NEW MEXICO Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WAMPLER, WILLIAM R.;DOYLE, BARNEY L.;SNOW, CLARK S.;SIGNING DATES FROM 20200803 TO 20200804;REEL/FRAME:053428/0753 |
|
AS | Assignment |
Owner name: U.S. DEPARTMENT OF ENERGY, DISTRICT OF COLUMBIA Free format text: CONFIRMATORY LICENSE;ASSIGNOR:NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA, LLC;REEL/FRAME:053610/0467 Effective date: 20200730 |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: APPLICATION DISPATCHED FROM PREEXAM, NOT YET DOCKETED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NOTICE OF ALLOWANCE MAILED -- APPLICATION RECEIVED IN OFFICE OF PUBLICATIONS |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: PUBLICATIONS -- ISSUE FEE PAYMENT VERIFIED |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |